In many applications for synchronous generators, it is highly desirable to eliminate brushes since they require somewhat frequent maintenance and/or replacement, as well as introduce noise into the power being generated. They are, perhaps, the single weakest point in the system. In order to eliminate brushes, brushless generator systems have been proposed wherein rotating permanent magnets on a dynamoelectric machine rotor act as a permanent magnet generator, or a PMG, generating alternating current in a stator winding. The alternating current from the PMG stator winding is rectified by a stationary rectifier and the resulting direct current is utilized to provide a magnetic field for a so-called "exciter " The magnetic field for the exciter is, of course, stationary meaning that current will be induced on a winding carried by the rotor which is typically a three-phase winding. This three-phase alternating current is then rectified by a rotating rectifier carried on the rotor to provide direct current for the rotating field of the main generator. As a consequence of the rotating field, alternating current is generated in a stationary stator winding of the main generator.
Systems of this sort are frequently employed in aircraft power systems and, as a consequence, they must be highly reliable with the rotary components having the ability to withstand high rotative speeds that may exceed 24,000 rpm.
Moreover, space and weight are always of concern in airborne systems and substantial efforts have been expended in developing machines of this sort. Illustrative examples may be found in the following U.S. Pat. Nos. 4,628,219 issued Dec. 9, 1986 to Troscinski; 4,745,315 issued May 17, 1988 to Terry, et al.; 4,794,510 issued Dec. 27, 1988 to Wege; and 4,806,814 issued Feb. 21, 1989 to Nold.
The Nold, Troscinski and Terry constructions generally employ so-called diode wafers, that is, semi-conductor wafers that are unpackaged, i.e., without housings and/or terminals, to develop compact assemblies. While these assemblies work extremely well for their intended purpose, considerable precision must be exercised in assuring that good electrical contact is made between the diode wafers and the various buses or other electrically conducting components utilized; and that tends to add to the cost of the assemblies.
Wege, on the other hand, utilizes packaged diodes which considerably cuts the expense of assuring good electrical contact between diode wafers contained within the packages and the respective terminals on the packages, since this is accomplished by mass production techniques in a reliable fashion Wege, however, utilizes such diodes in a way that the resulting rectifier assembly has a relatively large diameter. The present invention seeks to achieve the cost advantages that attend the use of the Wege type construction in a rectifier assembly of substantially lesser diameter.